As a production company we mostly focus on art, culture, and ideas. But to express those ideas we, like so many peeps, use a lot of expensive audio and video equipment. And every now and then we’ll pull a piece of gear off the back of the rack only to find it filled with nasty, corroded, often AA batteries.

So, as a public service to our own staff, and anyone else in this boat… why do batteries leak?

We’ve combined a little web research with a lot of personal experience and here’s what we think the story is. If you have different or better information, please drop a comment on this post and share the knowledge.

You’ll pretty much never find leaky batteries in gear you use regularly. But production habits can vary and sometimes expensive and valuable gear can fall out of the production loop for a while. When you reach down and open the battery compartments of expensive gear, cheap toys, flashlights, and all sorts of things, you’ll find half the stuff messed up with battery leakage and corrosion and half not. With no obvious pattern as to which gear this happens to. Sometimes your most expensive gear will the highest end batteries will be corroded, and your kid’s stupid talking plush toy with the cheapest batteries will be fine.

Modern batteries will keep on your shelf or in your fridge for a very long time. They’re sealed much better that the batteries of yore, and not likely ever to leak. Until… well… the batteries that leak, seemingly regardless of how “high end” or expensive they are, are batteries that are “deeply discharged,” far beyond normal useful range. So any gear, toys, flashlights, or anything else you use regularly will probably never have leaky batteries. Apparently some devices just have the tiniest resistance in them and cause batteries to very slowly discharge. Sometimes this is true on expensive gear. Perhaps more often than your kids’ cheap toys. So if a piece of gear falls out of use for a few months, your batteries can discharge… then deep discharge… then leak. Other gear that has no load whatsoever can have batteries in it for years with no leakage. Aside from learning the hard way, it seems difficult to predict what gear has a tiny load and what doesn’t.

You often see warnings to remove batteries for long storage, but we find that, sort of like that ex-partner of yours, you often don’t know at the time of the last kiss. that this is the last kiss. You only realize that later. So it’s hard to say, “Oh, this light meter or this wireless mic won’t be used for a few months now.” So even though it’s a pain, it’s a good idea to try to take cells out of all gear when returning it to the rack. This also puts you in the habit of putting fresh cells in gear before you use it.

Some rechargeables, like these "Hybro" NiMH cells are designed to have slower discharge when not in use.

ABOUT RECHARGEABLE CELLS
Rechargeables have two great features: higher capacity than disposables, and no leakage even when deeply discharged for a long time. And though they have higher initial cost they cost less over time. And they’re probably better for the environment. In spite of all these advantages, most production companies are wary of rechargeables because you’re often uncertain of their charge status. You can be diligent about this. But it’s somehow easy to get it wrong. And most rechargeables discharge pretty fast when not in use. Just as non-rechargeables won’t leak if you use them regularly, rechargeables will be charged if you use them regularly. But once again it’s the gear and batteries that you don’t use as often that cause all the problems.

Our advice then is to take cells out of gear when you return it to the rack. And if possible, to keep your production kit smaller and more regularly used. Yes, you often do need something different, but the more standard your production gear can be, the more familiar you’ll be with its operation and the more likely it will be to be properly maintained with fresh power cells in it.

Happy Production and may you never open a battery door to find leaky cells again! 🙂